The present disclosure relates to optical scanning devices in which an optical element is bonded and fixed to an optical base by means of a bonding agent, image forming apparatuses including such an optical scanning device, and optical elements.
In image forming apparatuses, such as copiers, printers, etc. that form images on a recording medium, such as paper by electrophotography, an image carrier of which surface is charged by a charger uniformly is subjected to exposure scanning by an optical scanning device to form an electrostatic latent image according to image information on the surface of the image carrier. The electrostatic latent image formed on the image carrier is developed with toner as a developer in a developing unit to be visualized as a toner image. Further, the toner image is transferred onto the recording medium through a transfer unit. The recording medium on which the toner image is thus transferred is conveyed to a fusing unit and then is heated and pressurized by the fusing unit to be subjected to fusing of the toner image. Thereafter, the recording medium to which the toner image is fused is ejected outside the apparatus. Upon ejection of the recoding medium outside the apparatus, a series of image forming operation is completed.
Incidentally, in the optical scanning device, light emitted from a light source, such as a laser diode (LD), or the like enters into a deflection means, such as a polygon mirror or the like through a collimator lens and a cylindrical lens. Then, the light deflected by the deflection means is imaged on an image carrier on a photoconductive drum or the like through an fθ lens. Subsequently, the image is subjected to exposure scan. In the optical scanning device, the optical elements, such as the collimator lens, the cylindrical lens, the fθ lens, etc. are directly fixed to an optical base by means of a bonding agent in order to reduce the number of parts.
Moreover, in order to maintain the high scanning performance of the optical scanning device, the optical elements, such as the fθ lens, etc. are bonded and fixed to the optical base with high accuracy. To do so, a positioning rib 119A is formed so as to protrude from an optical base 119, as shown in FIG. 6. An fθ lens 124, for example, abuts on the positioning rib 119A for positioning. Then, the positioned fθ lens 124 is fixed to the optical base 119 by means of a bonding agent 130.
However, in the case employing the fixing scheme as described with reference to FIG. 6, when the fθ lens 124 and the optical base 119 are thermally expanded by driving the optical scanning device or the like, the shear stress concentrates at bonding points. Because, (1) the fθ lens 124 cannot be moved relative to the optical base 119 because of abutment of the fθ lens 124 on the positioning rib 119A of the optical base 119; (2) the fθ lens 124 has a coefficient of linear expansion different from the optical base 119; and the like. As a result, the shear stress may overpower the bonding strength to cause the fθ lens 124 to come off from the optical base 119.
By contrast, a method as shown in FIGS. 7A and 7B has been proposed as still another technique for fixing an fθ lens.
Specifically, FIGS. 7A and 7B are cross sectional views showing the method for fixing an fθ lens. In the fixing method explained with reference to FIGS. 7A and 7B, in order to fix an fθ lens 224 to an optical base 219 by means of a bonding agent 230, the fθ lens 224 is positioned accurately by using a jig 250, as shown in FIG. 7A, and is bonded to the optical base 219. Then, the jig 250 is removed, as shown in FIG. 7B.